Known laser surgical devices, many of which are applied by direct contact with tissue to be affected thereby, often utilize emitted laser light energy for ablation or vaporization of tissue. Laser light energy is also sometimes used as a supplement with an otherwise traditional scalpel-type sharp-edged cutting implement. An example of such a device is disclosed in U.S. Pat. No. 4,126,136, to Auth et al. This photocoagulating scalpel system includes a scalpel having a physically sharp transparent blade for forming 20 an incision, with a laser energy source optically coupled to the blade through a low-loss fiber optic wave guide. Laser light is emitted through the sharp edge of the blade for coagulating blood adjacent the incision. The material used for such a sharp scalpel blade is quite hard, but the required sharpness may be difficult to maintain.
Another recently-proposed device is described in U.S. Pat. No. 4,627,435, to Noskin, in which a surgical knife includes a handle supporting a diamond blade coupled to a Nd/YAG laser. See FIG. 1 hereof. The surgical diamond knife 1 has a handle 3 supporting a diamond blade 4 connected to the Nd/YAG laser 5 by optical fibers 6. FIG. 2 illustrates another embodiment of the same invention, wherein a relatively long slim handle 13 houses an optical fiber bundle (not shown) coupled at one end to a wedge-shaped diamond blade 14. The cylindrical body portion 13 of this knife is connected at a proximal end to a sheath 16 which protects the bulk of the length of the optical fiber. See FIGS. 3 and 4 for Hoskin's shapes for laser energy delivering diamond tips 14 and 24. In each case, the laser energy-delivering diamond tip element has a sharp edge. Laser light provided to such tip elements is internally reflected through the body of the tip element from the optic fiber to the cutting edge to enable the surgeon to more readily make his incisions.
In yet another example of the art, U.S. Pat. No. 4,693,244, to Daikuzono, teaches a medical and surgical laser probe in which laser energy from an optical fiber is conveyed by internal reflection within tapered tip elements 11 (in FIG. 5), or 13 (in FIG. 6) to specifically formed energy-delivery zones at their frontal pointed ends. When certain geometric parameters are satisfied, laser energy can leak out from the tapered side faces of rod member 11 to reach tissue 12, as depicted in FIG. 5, so that the flow of laser energy density emitted from the narrow tip end face is lowered. This would make incision of the tissue 12 difficult. Also, the laser energy which leaks from the tapered face irradiates tissue at a distance and this may be undesirable. However, when the refractive index of the tip element and its geometry both satisfy conditions specified in this reference, a much higher energy density is attainable at the tip end which is shaped and treated to deliver thermal energy generated by partial absorption of the laser light energy in a thin coating, with another portion of the available laser light energy emitted through the tip end.
In devices of the type discussed hereinabove, there are various inherent structural and operational limitations encountered by a user, e.g., that the laser energy delivery end must be maintained physically sharp. Furthermore, since the energy is delivered through a very small volume of the tip element at the sharp edge or pointed tip, the surgeon/user must exercise extreme care in controlling the rate at which laser energy is being delivered as he or she performs a variety of interrelated functions, i.e., makes incisions, cauterizes cut blood vessels, and coagulates leaked-out blood so that it does not interfere with accurate viewing of or access to the surgical site.
There is, accordingly, a need for a sturdy, blunt, i.e., physically non-sharpened, tip element by which laser light energy can be utilized precisely to selectively perform incisions, to cauterize blood vessels, and to coagulate blood.